Multi-cavity tubes for air-over evaporative heat exchanger
a heat exchanger and multi-cavity tube technology, applied in indirect heat exchangers, refrigeration components, lighting and heating apparatuses, etc., can solve the problems of lowering the effectiveness of evaporative heat exchangers, and achieve the effects of improving thermal capacity, increasing weight and cost, and improving efficiency
Active Publication Date: 2020-02-25
EVAPCO
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Benefits of technology
This invention serves to solve the problem of increased weight and cost with incremental improvements in capacity by improving the thermal capacity while decreasing the cost for equivalent thermal capacity with a special tube shape and pattern that increases the prime surface area in contact with the airstream thereby improving thermal capacity, at the same time decreasing the thickness of the heat exchanger tubes thereby decreasing the cost for equivalent thermal capacity. The effective diameter of the tube is reduced by the design of the invention, which allows the tube wall to be reduced in thickness for the same internal pressure. The open air face area to tube face area ratio determines to a large extent the effectiveness of the heat exchanger. If this ratio is too low, the heat exchanger will have an undesirable airside pressure drop, lowering its effectiveness in an evaporative heat exchanger. This effect is more pronounced in evaporative heat exchangers than in a dry air heat exchanger because of the water-air interaction. The tube shape and pattern of the invention serves to keep this ratio equal to or lower than conventional heat exchangers of the same volume (i.e., coil volume, that is, the volume defined by the outer dimensions of the coil, L×W×H) while increasing the surface area of the coils. The combination of increasing the coil surface area, reducing the tube wall thickness, and maintaining or decreasing the airside pressure drop using the new tube design of the invention serve to create a heat exchanger with superior thermal efficiency and cost effectiveness.
Therefore, there is provided according to various embodiments of the invention multi-lobed tubes that may be used in place of single round or elliptical-shaped tubes of prior art heat exchangers. These multi-lobed tubes are tall and narrow in vertical cross section. The multi-lobed tubes may have 2, 3, 4 or more lobes per tube. The multi-lobed shape allows the tubes to have a smaller air-face profile and thinner wall while maintaining the working pressure limit and outside surface area per tube. The narrow air-face profile also allows many more tubes to exist in the same heat exchanger volume while maintaining or decreasing the open air face area to tube face area ratio to maintain or decrease the airside pressure drop and maintain or increase the airflow volume per horsepower. Heat exchangers having the tube design of the present invention will work equally well as fluid coolers or refrigerant condensers.
Problems solved by technology
If this ratio is too low, the heat exchanger will have an undesirable airside pressure drop, lowering its effectiveness in an evaporative heat exchanger.
Method used
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Embodiment Construction
FIGS. 1 and 2 show an induced draft single cell evaporative cooler according to the prior art. Fan 101 draws air into the unit and forces it out the top of the unit. Below the fan is a water distribution system 103 that distributes water over the tube coil 105. The tube coil is made of an array of serpentine elliptical tubes 107. Each length of tube 109 is connected at its ends to an adjacent higher and / or lower tube length by a tube bend 111. Process fluid to be cooled enters the tubes via an inlet header 113 and exits the tubes via an outlet header 115. Beneath the tube coil is the plenum 117, where air enters the unit and the water that is delivered to the unit via the water distribution system 103 is cooled via direct heat exchange with the air, collects at the bottom and recirculated to the top via water recirculation system 119.
FIGS. 3 and 4 shows a conventional evaporative heat exchanger elliptical tube 107 of the type used in the prior art heat exchanger of FIGS. 1 and 2. A ...
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An air-over evaporative heat exchanger with multi-lobed or “peanut” shaped tubes replacing conventional round or elliptical tubes. The tubes have a narrow horizontal cross section and tall vertical cross section to allow the multiplication of surface area in the same coil volume while maintaining or increasing the open-air passage area. This configuration allows the coil to have an overall external heat transfer coefficient much higher than a conventional coil, while the tube shape allows the use of thinner material, reducing the weight and cost of the heat exchanger.
Description
BACKGROUND OF THE INVENTIONField of the InventionThis invention relates to evaporative air-over heat exchangers.Description of the BackgroundIt is well known that elliptical tubes work well for evaporative heat exchangers. Increasing the heat exchanger tube density works well for systems that have no airflow over the coil, while increasing the external surface area using extended fins works well in systems that have airflow over the coil. However, both of these methods increase the weight of the heat exchanger coil and consequent cost per heat exchanger compared to conventional tube-coil designs since the tubes are required to have a minimum wall thickness to operate under internal pressure without deforming.SUMMARY OF THE INVENTIONThis invention serves to solve the problem of increased weight and cost with incremental improvements in capacity by improving the thermal capacity while decreasing the cost for equivalent thermal capacity with a special tube shape and pattern that increa...
Claims
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IPC IPC(8): F28D3/02F28D3/04F28F1/06F28D1/047F28C1/14F28F1/02F28D15/00F28D21/00F28F25/00
CPCF28C1/14F28F1/02F28F1/06F28D1/0478F28D3/04F28D3/02F28D2021/0063F28F2025/005F28D15/00F25B39/02F28D1/024F28F1/10
InventorKANE, JEFFREYVADDER, DAVEY JOE
OwnerEVAPCO